If positive results, where's me gold?

[Boarteats]

Motivation for this question is that I'm collecting rock samples for my first ever assay purchase. Ideally, I'd like to filter out low probability material.

I've had pretty good results using my Falcon MD20. When I receive a false positive, finding the culprit is typically pretty straightforward. ...at least up to now.

I'm currently exploring an area with highly mineralized sedimentary rocks like the ones in the very short video link. Lots of iron oxide. The samples seen in video were roasted. These rocks often elicit what I believe is a positive response from my Falcon MD20 (see link to short video). However, I don't yet understand why. Crushing and panning samples often times doesn't reveal any identifiable gold or anything else that explains my detector's response.

So, couple questions for those of you with much more knowledge and experience than I.

1. In the linked-to video, I scan an exemplar rock sample with an MD20. I believe that the detector is providing a positive response indicating presence of gold, silver, copper, or some other nonferrous metal. Am I, in fact, interpreting the detector's response correctly?

2. If yes to #1, where's me gold? More specifically, why might I receive such a response in cases where I cannot identify any ostensibly responsible mineral? Crushing and panning samples only reveals some magnetite, sand, and occassionally specs of material that looks like gold but is too light in the pan to be gold.

Might there be gold in rocks that the MD20 can detect but I cannot see even when using 50x magnification?

Hope this post isn't too convoluted. Apologies for link. I don't see a way to upload the actual video.

https://drive.google.com/file/d/131-bfQQ7YHg9ZzHbbCqn0g23HNmjkMmW/view?usp=drivesdk

 

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[arizau]

I'm no expert but.... maybe what you have contains, or created by roasting, iron oxide and are/may be "hot rocks" with a large enough concentration of the iron oxide to set your detector off. See here for explanation. https://www.metaldetectingworld.com/hot_rocks.shtml. Regular detectors can sound off to them so it makes sense that the md20 would too as it also is a metal detector.

 

[Clay Diggins]

No metal detector can detect any particular type of metal with any confidence. Any successful experienced gold detectorist knows that you have to dig every target no matter what signal your detector shows.

I personally know of three very large near surface gold nuggets that have been passed over for years by detectorists that believe they can discern a gold signal from any other signal. One was a well known "can" that was in the middle of a trail in a heavily detected area, that turned out to be a 3+ ounce large flat nuggets less than four inches deep.

I've seen the claims for the Falcon for years. It's just marketing. Much like the marketing for many other detectors.

Dig every target.

Heavy Pans

 

[Treasureman25]

Dig dig dig!

 

[galenrog]

The Falcon is not unlike other pinpointers. A few design changes, but essentially the same. I have had one for several years, and find it a helpful tool, and only a tool.

I do do not know how long you have had yours, but six months to a year of field use is what a good operator needs to understand what any detector is trying to say. The ring adjustment confuses some, as does the difference in tone quality when tip approaches or is pulled from target. You will either learn to use it properly (you may have already) or you will not.

A few hours from my home the targets are challenging. Due to pockets of high grade copper, nickel, and other metals, many using detectors as prospecting tools get easily confused. The area still has impressive gold pockets leading many, including some experienced prospectors to incorrectly assume what their tools are telling them.

An experiment I used when learning the MD20 was to set up samples of copper filings, brass filings, nickel filings, fine placer gold, and various iron compounds. The test was to identify what was with the black sand in both dry pans, and wet. After more attempts than I care to count, I was able to successfully identify, at a rate of about 60%, copper, brass, nickel, and gold. Lead and some lead compounds were always a challenge. Perhaps setting up a similar test would help you better identify what you have.

Anyway, just my two cents on the matter. Like any other tool, operator experience is the key.

Time for more coffee.

 

[oneguy]

welcome to the world of the hot rock......

 

[Boarteats]

I'm no expert but.... maybe what you have contains, or created by roasting, iron oxide and are/may be "hot rocks" with a large enough concentration of the iron oxide to set your detector off. See here for explanation. https://www.metaldetectingworld.com/hot_rocks.shtml. Regular detectors can sound off to them so it makes sense that the md20 would too as it also is a metal detector.

Arizau, this article is EXACTLY what I needed. Thx!! Maghemite, magnetite, bornite are not uncommon in my target area.

 

[Boarteats]

The Falcon is not unlike other pinpointers. A few design changes, but essentially the same. I have had one for several years, and find it a helpful tool, and only a tool.

I do do not know how long you have had yours, but six months to a year of field use is what a good operator needs to understand what any detector is trying to say. The ring adjustment confuses some, as does the difference in tone quality when tip approaches or is pulled from target. You will either learn to use it properly (you may have already) or you will not.

Galenrog, have had detector for less than 2 months. I like your approach of setting up targets of various materials and training yourself on detector response for each target type. Would be nice to have a catalog of false positive minerals.

 

[galenrog]

Sadly, after a stroke, much of my equipment was sold, and many notes given away. As far as cataloging false positive ores and minerals, experience is still a great teacher. That and a field chemistry set and a good guide on mineral identification.

Time for more coffee.

 

[Goldwasher]

Falcon is a very limiting metal detector. For overall hunting. it's best on known lode material especially for paring down pieces and hunting gold in them.

 

[Goldwasher]

No metal detector can detect any particular type of metal with any confidence. Any successful experienced gold detectorist knows that you have to dig every target no matter what signal your detector shows.

I personally know of three very large near surface gold nuggets that have been passed over for years by detectorists that believe they can discern a gold signal from any other signal. One was a well known "can" that was in the middle of a trail in a heavily detected area, that turned out to be a 3+ ounce large flat nuggets less than four inches deep.

I've seen the claims for the Falcon for years. It's just marketing. Much like the marketing for many other detectors.

Dig every target.

Heavy Pans

Combine that with how many people trust discrimination.

With a GB2 in Iron disc. mode.

You can take a concrete form nail. Hold it with a large piece of gold.. like multi DWT. It will null out both targets with discrimination.

Make all sorts of false ID on a digital display. If its a machine with one.

I dig all targets.. but , sometimes after walking away and coming back. I can only digest so much can slaw. In one spot before I have to look for other CABBAGE!!

 

[Boarteats]

The above-referenced article describing hot rocks had the info that I needed. More effectively adjusting ground balance and paying closer attention to quality/nature of ostensibly positive detector responses have greatly improved my experience with the MD20. Graphite is still a pain but not much that one can do about it, I believe. Not sure if I can find mitigations for false negatives given the copious amounts of iron oxides and the such in the rocks.

I'd love to have a goldbug or similar detector for searching gravel piles but can’t justify the cost since this is just a fun hobby for me.

 

[Johnnybravo300]

Steel toe boots?

 

[Rail Dawg]

When we were told 100 hrs of detecting time before we even began to become proficient they were right.

Chuck